Up to now, stents have been used to widen a lumen such as a blood vessel and then to maintain the resultant size of the lumen. Expansion of the stent may be done by various methods such as, for example, a balloon expansion process, a self-expansion process utilizing a shape memory material, a mechanical expansion process and the like. Among them, it is general practice to use a balloon expansion process. In the balloon expansion process, the stent is introduced into a desired site of a lumen in the living body along with a balloon catheter, and then expanded by inflating the balloon, thereby widening a size of the lumen. Next, the balloon is deflated and removed from the site, leaving the expanded stent in place.
The stent generally comprises lumen size-holding portions for widening and holding a size of the lumen of a blood vessel, and connecting portions for connecting these lumen size-holding portions in a longitudinal direction thereof. The stent maintains its shape after being expanded.
Various types of stents have been suggested in Japanese Patent Gazette. For example, JP-A H06-181993 discloses a stent comprising a plurality of cylinder components independently expandable in a radius direction, which are arranged around a common axis and connected to one another. JP-A S62-231657 discloses a stent comprising a tubular-shaped member expandable in a radius direction thereof and being formed by a plurality of intersecting elongated members. JP-A H08-155035 discloses a stent comprising at least two circular members each comprising a signal wire bent to form segments that are substantially straight and un-overlapped and are integrally connected at turns of the wire. JP-A H10-503676 discloses a stent comprising a tube having a patterned shape which has first and second meander patterns having axes extending in first and second directions. JP-A H11-505441 discloses a stent of open structure comprised of end-connected struts making up the parts with angular interconnects between the parts.
The aforementioned stents of the prior art have been improved in flexibility to some extent, but it is rather difficult to say that they have a sufficient flexibility. Since these stents become a burden to the inner wall of the blood vessel adjacent to edge portions of the stent, there is a fear of causing obstruction or constriction in the lumen. Further, if the lumen is of a three-dimensionally meandering structure, it is occasionally difficult to advance the stent to the desired site within the lumen. In addition, there is a fear of injuring the blood vessel during advancement of the stent to the desired site.